TODO-PLUS-FIXME-ton

[jurgenvinju]

There is a sizeable number of detailed TODO's and FIXME's in the clair code; propose to make a plan to tackle these one-by-one:

• [ ] create a list of TODO's and FIXME's in the code of Clair and list them here.
• [ ] fix each TODO and FIXME, possibly adding test cases for the newly covered features
• [ ] release a new version of clair